1. Field of the Invention
The present invention relates to devices for performing percutaneous arthroscopic and other endoscopic surgeries and, more specifically, to surgical cannulae.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Traditional minimally-invasive arthroscopic surgeries are performed using a cannula device to penetrate small incisions in the patient's skin and outer tissue, creating a port through which surgical tools may be passed to allow access to the underlying structure of interest. For example, in shoulder arthroscopy, the procedure is performed through “portals” in the patient's skin. These portals are formed from small incisions, generally about ½ of an inch to an inch long in the skin, and are located over particular areas of the joint that the surgeon will need to operate upon. Cannulas are then inserted into the portals so that instruments can easily be placed in the shoulder joint. Shoulder arthroscopy itself involves inserting a specially designed video camera with a very bright fiber optic light source into the shoulder joint so that the important parts of the joint can be seen. Instruments that have been specially designed to remove inflamed tissue, attach sutures to bone, and repair torn tendons and ligaments are then used to operate inside the shoulder.
The area between the skin tissue and shoulder joint is quite small. Consequently, it is necessary to “inflate” the area by pumping an irrigation fluid (e.g. saline) into the joint under pressure. In laparoscopic surgical procedures, carbon dioxide in gaseous form may be utilized as an insufflating agent to perform a similar function. The pressure produced by the irrigation fluid pushes the tissue outward from the joint and allows greater room for manipulation of the arthroscopic camera and other surgical tools. However, the actual working angle of the tools is ultimately determined by the length and inner diameter of the cannula. Heavy patients or patients with large amounts of skin and other tissue covering the joint require a longer cannula to penetrate the tissue sufficiently for the procedure. This increased cannula length decreases the working angle of the tools at the joint, limiting the ability of the surgeon to perform the procedure. Although this angle may be improved by increasing the inner diameter of the cannula, there are realistic limits on the useable diameter. For example, the diameter can only be increased by a small amount or else it would effectively eliminate any benefit of conducting the arthroscopic procedure as the portal size could become the equivalent of a large incision as performed in traditional surgery.
Manufacture of cannula devices incorporating shape memory alloys embedded therein can be somewhat costly in practice. Specifically, the molding of shape memory alloys into the polymers of a cannula device can increase the costs associated with the cannula device thereby driving up the overall medical procedure costs. Moreover, disposal and possible recycling of used polymers is readily simple unless non-polymer materials are also present.
What is needed is a cannula device that is capable of compressing the tissue through which it penetrates, that is relatively simple to insert and remove so as to minimize tissue damage to the patient, and that includes a novel means for incorporating a shape memory alloy into its design that is easy to store, use, remove, and reuse. The retractable cannula disclosed herein satisfies these needs and others as will become apparent to one of ordinary skill after a careful study of the detailed description and embodiments.
The above figures are provided for the purpose of illustration and description only, and are not intended to define the limits of the disclosed invention. Use of the same reference number in multiple figures is intended to designate the same or similar parts. Furthermore, if and when the terms “top,” “bottom,” “first,” “second,” “upper,” “lower,” “height,” “width,” “length,” “end,” “side,” “horizontal,” “vertical,” and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawing and are utilized only to facilitate describing the particular embodiment. The extension of the figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiment will be explained or will be within the skill of the art after the following teachings of the present invention have been read and understood.